Adding support for context menus.

[defiantnerd]

• adding host side context menu functions
• extending the calling structure/lifecycle management of plugview

[baconpaul]

@defiantnerd i reviewed the code and see nothing I’d change. That lifetime mismatch is indeed painful but I think you have it correct. Once the formatting is fixed I Jin his should merge to next

[defiantnerd]

Thanks, @baconpaul